The application of high heat input welding such as electrogas arc welding (EGW) has been demanded for the efficiency in steel bridge fabrication. The influence of steel chemical compositions and welding heat input on heat affected zone (HAZ) toughness was investigated in EGW joints of SM570 steel. From the view point of the HAZ toughness at -5°C, low C-Ti added SM570 steel is available to the EGW having heat put up to about 13kJ/mm. The formation of HAZ microstructure is mainly influenced by the chemical compositions and the welding thermal cycle represented by cooling time from 800°C to 500°C, and consequently, the microstructure dominates the toughness.

View full abstract

The purpose of this study is to investigate the relation between the objective function and the accuracy in identification of the parameters in the horizontally laminated ground model using vertical array records of ground motions. The numerical analysis of the identification is generally carried out in the frequency domain, supposing one-dimensional multiple reflection of shear wave. The spectral ratio of ground motions is often used as the target. And the parameters of the ground model are to be optimized so as to minimize the residual between the spectral ratio and the transfer function of the ground model. However, the bad influence of smoothing of spectra has often been indicated. On the other hand, the numerical analysis has recently been applied in which the time history of recorded ground motions is the target. In this paper, a new objective function is proposed, and the accuracy of identification, the shape of objective functions and the ifluence of initial values are compared.

View full abstract

This research has aimed to understand the behaviors of the crack of the RC deck slab caused by a negative bending in the middle supports of continuous composite gider bridges. For the determination of stress and strains in cracked regions, the effect of tension stiffening of concrete on stresses in reinforcement has to be taken into account. It was confirmed from the fatigue tests that the crack width approaches to a certain value with the increase of the number of repeated cycles.

View full abstract

Many cases of fatigue damage on orthotropic steel deck structures were reported. This paper addressed a control of the fatigue crack occurrence on the deck plate and trough rib. The crack is the most serious one, because it causes depression of road surface and functional depression of an orthotropic steel deck. The investigation was performed by 3-dimensional fine meshed FEM and Effective Notch Method. This paper is also interesting from the view point of the practice of effective notch stress method. As a result of parametric analysis; parameters are trough width, deck plate thickness and welding condition, we propose the suitable geometry of deck plate and trough ribs.

View full abstract

The necessity of assessing the durability of structures such as bridges and offshore structures has arisen recently. It is obvious that the maintenance of infrastructures has become a key issue to assure the desired performance in operational condition and to prolong the life of structures. As for the life cycle performance of the steel elements in the marine atmosphere, in particular, the damage due to corrosion is important rather than that by fatigue. Investigated herein is the effect of the surface profile of corroded steel plates on the compressive strength by the elasto-plactic finite displacement analysis, by using the ficticious surface profile as well as the surface profile measured for the corroded steel pipes subjected to the corrosion exposure in the field under severer marine environment for about 20 years. The simple strength evaluation is proposed by considering the plate thickness variation in the smallest cross section.

View full abstract

Welded joint between main girder web and lateral girder flange is usually subjected to bi-axial stresses that are stress on the web due to bending moment and stress on the flange induced by load distributing action of lateral girder. Weld toes on the web and the flange have been considered as fatigue failure origin. Influence of bi-axial stress on fatigue strength of the web has been already reported. In this study, for the purpose of examining the influence of bi-axial stress on fatigue strength of lateral girder flange welded to main girder web, fatigue tests have been carried out using model specimens. As the result, fatigue strength of the flange has lowered due to stress on the web, and the influence could be evaluated by stress concentration factor.

View full abstract

The slip capacity of HSGB joints with thickness difference between jointed plates is investigated by both FEM analysis and simplified formula derived from beam theory considering shear deformation. The accuracy of FEM analysis and proposed formula is examined by the comparison to the experimental data. Summarizing the FEM results and characteristic figures by simplified formula, following proposal is suggested for the design and fabrication of HSGB joints. The allowable thickness difference between jointed plates should be limited within 1mm for ordinary thickness splice plates. For thick splice plate beyond 16mm, the inner edge distance should be taken larger value than 40mm corresponding to splice plate thickness adding thickness difference limitation 1mm.

View full abstract

The mechanism of noise generation and noise control for modular expansion joints were investigated in experiments on a full-scale model of the joint. Noise and vibration of the joint model were measured when a car was runnig over the model. It was concluded, based on this measurement together with tests of the acoustic and dynamic characteristics of the joint model, that the noise from the top of the joint could be attributed to a sudden change in the air pressure in the gaps formed by the sealing rubber elements, and the noise from the bottom was probably caused by sound radiation from vibration of the middle beams. Effects of some proposed noise control measures were also investigated experimentally.

View full abstract

Damage to buried water-supply pipelines in the non-liquefiable ground from the 1995 Hyogoken-Nambu earthquake was first compared with calculation results from the relevant seismic design code. The results showed that the damage occurred even if there was a margin of safety of about 2. In addition, the earthquake-induced displacement of the non-liquefiable ground was next evaluated using results from survey, strong motion observation and numerical simulation in the near field of the 1995 earthquake. It was found that the dynamic displacement and the permanent displacement were significant not only on the surface layer but also at the engineering bedrock.

View full abstract

This paper presents a general modeling in X-FEM (eXtended Finite Element Method) and its synthetic evaluations in two-dimensional linear fracture mechanics. The modeling consists of three parts: (1)curved crack and integration area, (2)area considering singularity around near crack tips and (3)method for coordinate transformation by mapping on the area which has C-nodes and J-nodes. The results have shown a good accuracy of the proposed method in evaluations of stress intensity factors and crack growth simulations with limitation of path independent M-integral to a curved crack.

View full abstract

A cyclic bi-directional loading experiment is carried out to examine the ultimate seismic behavior of thin-walled stiffened rectangular columns by using the accurate 3D-loading system. So-called a cyclic diamond load is adopted as one of the severest bi-axial loading patterns for rectangular columns. The results obtained from the experiment are also used to confirm the applicability of the nonlinear FEM shell analysis where the three-surface cyclic plasticity constitutive model is implemented. With the nonlinear FEM analysis as well as the experimental results, the seismic performance of the stiffened rectangular columns under cyclic bi-axial loading is extensively examined in comparison with that under in-plane cyclic loading. Finally, formulas are derived to evaluate the seismic performance of arbitrary rectangular steel columns subjected to the cyclic bidirectional loads.

View full abstract

Three-dimensional computational fluid dynamics are performed to investigate the flow around two circular cylinders in tandem arrangements at a high Reynolds number. The center-to-center space of the cylinders is varied, and the flows and the fluid dynamic forces obtained from the simulations are compared with those in the literatures on experimental studies. Special attention is paid to the interference of the vortices shed from the upstream cylinder and those from the downstream one. The effects of the interference on the fluid dynamic forces acting on the downstream cylinder are clarified throughout simultaneous observations on the fluid behaviors and on the fluctuations of the cylinder-surface pressures.

View full abstract

We examine the crack paths in concrete due to reinforcement corrosion and investigate their influencing factors by performing numerical simulations of propagating cracks. In order to accurately simulate the initiation and propagation of cracks, we enhance the finite cover method (FCM) so as to work with regularly structured mesh without remeshing and characterize nonlinear behavior of process zone fracture by means of the cohesive crack model. The method enables us to not only reproduce the modes of crack paths reported in experimental studies by combining the mechanically correct model of reinforcement corrosion, but also evaluate the effect of initial condition and use environment of global structure for propagating cracks in local structures.

View full abstract

This paper presents the test results of corrugated steel web girders under a mid-span concentrated loading. Four different trapezoidal corrugation configurations, including a flat web, were used. And laterally unbraced length of girder was chosen to three span lengths for each cross-section. All specimens were failed due to lateral-torsional buckling. The test results of buckling behavior and ultimate strength were compared with the analytical results using the finite-element program DIANA. It was found that the contributions of the corrugated web to lateral buckling load obtain for the longer girders with large wave height. The ultimate strength can be estimated using the resistance moment of two flange sections and the modified slenderness ratio accounting for flexural and torsional rigidities of corrugated web. The ultimate strength curve was also investigated based on existing test data and parametric analyses.

View full abstract

Once a continuous girder bridge becomes unseated at one pier, the girder is likely to collapse due to bending or shear forces. In this study, the necessary capacity of an unseating prevention cable to prevent the girder of a continuous girder bridge from collapsing was investigated using static and dynamic analysis. The static analysis verified that an unseating prevention cable designed using the present design procedure had sufficient capacity to resist the excessive bending moment and shear force caused by falling of the girder. The dynamic analysis showed that a part of the girder yields due to the large bending moment if a low stiffness cable is used as the unseating prevention cable.

View full abstract

This paper deals with experiment of the dynamic motion of an elastic floating bridge in winds and waves using a wave generator tank installed in a wind tunnel. The ends of the superstructure are moored by mooring devices with nonlinear restoring force characteristics in the horizontal direction transverse to the bridge axis. From the experiments, it is found that the dynamic motion of the floating bridge may be affected more strongly by the wave force than by the wind force. Moreover, the floating bridge is moved to the leeward side by the wind force and the dynamic motion by the wave force is done in the place after it moves. The analytical results with the computer program by the authors (Fumoto et al.,2006) for the dynamic elastic behavior of the floating bridge in waves are found to have good correlations with the experimental ones.

View full abstract

In order to realize super long span suspension bridges with longer main span than the Akashi-Kaikyo Bridge, a bridge should economically be designed with excellently aerodynamic stability. To achieve our economic goals, a hybrid suspension bridge that combines suspension and cable-stayed systems has been focused. To improve aerodynamic properties, di-box-girders are applied in the center part of the main span of this hybrid suspension bridge. And narrow mono-box girders are applied near the towers to restrict the mass of the bridge. A hybrid suspension bridge with mono- and di-combined deck girders is proposed to improve aerodynamic stability and economy. The aerodynamic stability of the proposed bridge was investigated by conducting wind tunnel test. The test result shows the high possibility for the improvement of the aerodynamic stability.

View full abstract

The accuracy of dynamic solutions of Timoshenko beam theory is not assured for higher frequencies above the critical frequency determined by the slenderness ratio and material constants of beam. In this paper, looking upon the free vibration of beams as the stationary motion of the transverse wave propagation, we discussed the accuracy of natural frequencies determined by Timoshenko beam theory by comparing with the Pochhammer-Chree theory. As the result, we have showed that the stationary waves with higher frequencies above the critical frequency, except for simple beams, are generated by the superposition of two transverse elastic waves with the phase velocities of the first and second modes, and that the accuracy of the second phase velocity governs the accuracy of Timoshenko beam theory. Consequently, we need to be careful to determine the applicable range according to the slenderness ratio of beam when we apply the Timoshenko beam theory for higher frequencies above the critical frequency.

View full abstract

Since the flutter phenomenon is one of the divergent oscillations, the flutter stabilization is the most important subject in the design of the long-span bridge girders. However, some subjects about flutter mechanism are remained to be clarified. In the previous study, the author clarified branch switching characteristics of coupled flutter and torsional flutter of structural sections by use of Step-by-Step analysis. In this study, complex eigen-value analysis and Step-by-Step analysis are carried out with changing the ratio of torsional frequency to heaving one. Then, the branch switching characteristic is investigated in detail. Furthermore, 2DOF free vibration test is carried out to verify the result of analyses.

View full abstract

In this study, the real-time hybrid earthquake loading test system basing on the velocity based loading concept was developed. The test system utilizes the concepts of the real-time hybrid loading test method and the substructure technique to combine the loading process of rubber bearing specimens and numerical modeling of bridge columns and girders. A series of real-time hybrid loading tests of rubber isolators (NR, HDR, and HDR-S) were conducted. The objective of this study is to pursue accurate prediction of the dynamic response and base isolation effects of rubber bearings under realistic earthquake conditions. Specially, the base isolation effects of HDR-S (supper-high-damping rubber bearing) were discussed. Through the test results, it is clarified that the HDR-S has more base isolation effect than HDR and NR.

View full abstract

The guideline for steel bridges by Japan Road Association requires that the heat input of welding for SM570 steels should be at most 7kJ/mm. However, the recently developed steel called BHS500 (Bridge High performance Steel) has made it possible to use high heat input welding such as 10kJ/mm or more without sacrificing the qualities of welded joints. In this paper, we conduct the electro-gas welding of 12 and 18kJ/mm heat input to examine the charpy impact and fracture toughness properties of the welded joint. The results show that the welded joint of BHS500 meets the requirement by the guideline and that the high heat input welding such as 18kJ/mm can be applied to BHS500.

View full abstract

Liquid sloshing of oil storage tanks caused by Tokachi-Oki earthquake in 2003 gave severe damage to oil tanks in Tomakomai area. The purpose of our study is to establish damping method against liquid sloshing so that destruction and sink of floating roofs of the oil tanks can be prevented. In this paper, we propose the buffer using viscoelastic materials as anti-liquid sloshing measure and have confirmed liquid sloshing damping effect of the buffer by φ0.6m tank model shaking table experiment. It is suggested that the buffer is an effective damping method for liquid sloshing.

View full abstract